Many dietary approaches for weight loss are currently available to the public, and each purports to offer advantages. However, there is little scientific evidence to indicate how these dietary approaches, some of which vary markedly in the foods that they limit or exclude, affect biomarkers for breast cancer risk. In particular, it is not know whether the critical factor in relation to weight and breast cancer is simply weight loss (negative energy balance), irrespective of the manner in which it is achieved, or if certain dietary approaches affect breast cancer risk biomarkers more favorably than others. Published data from our laboratory suggest that dietary pattern does matter, and therefore the goal of this study is to investigate the effects of two popular weight loss dietary approaches that differ in the extent to which they limit carbohydrate or fat consumption (with effects on dietary glycemic load) compared to a usual care group on prognostic markers for cancer recurrence in postmenopausal breast cancer survivors. The investigators hypothesize that in addition to the anticipated effects of fat loss on circulating levels of bioavailable sex steroid hormones, that the effects of excess fat on breast cancer prognosis can be attributed to three interrelated metabolic processes that affect cancer progression: altered glucose metabolism, chronic inflammation and excessive cellular oxidation.